Please answer these questions seperatly:

1. Which car is faster? (Type SS or Super Nitro)

2. Which car has better handling?

3. Which car is overall better quality?

Personally, I'd stray away from HPI, even just for bashing. If you want a good on-road car Team Associated's Nitro TC-3 is good, and if you want to try belt drive (I perosonally like it better) than the Team Trinity Reflex NT is great too.
Super Nitro is slightly larger than the SS, however I'm not sure which one goes fast as I've never seen a Super Nitro run

I personally Like Hpi. I own a hpi nitro mt and the thing is great! The only downer to hpi is that the 15 fe runs hot so think of a new engine down the road.. Trust me it turns the car from zero to hero! I dont know about the ss or the super nirto but i bet the Pro 3 would give you the speed' you want. I've played with one and its great. Dont think that team associated cars are bad but they are also Really good cars on the market. I'd say stay away from kyosho, good cars, parts are hard to get.! good luck